This invention relates to improving the combustion efficiency of automatic furnaces. More particularly, this invention relates to an improved method and apparatus for exhausting waste combustion products from an automatic, gas-fired furnace system, to reduce the amount of valuable heat and fuel escaping with the combusted gases.
Furnace systems, such as those used in residential houses, small and large buildings, industry and the like, are often fueled with fuels, such as oil, coal, natural gas and the like. Such furnace systems produce combustion products or flue gases which must be disposed of in the atmosphere through flue gas ductwork.
One disadvantage of such furnace systems is that such flue or combustion gases retain or otherwise have a significant amount of valuable heat, and heat-producing components, derived from fuel combustion. Unless such heat, actual and potential, is recovered, it escapes to the atmosphere and reduces the overall fuel efficiency of the furnace system.
Many devices have been suggested by the prior art to recover some of this energy from furnace system combustion gases. Often, these systems are mere auxiliary heat exchangers, which while being complex, expensive, requiring substantial maintenance, and frequently being too bulky to be compatible with the space requirements, do no more than recover a part of the sensible heat without recovering the latent heat (unspent fuel potential in the exhaust gases). Thus, the average building owner, or resident, who has a furnace system for heating purposes, loses a significant amount of available energy when the combustion gases are exhausted to the atmosphere. Such losses result in reduced furnace efficiency and increased fuel consumption, for a given level of useful heating produced. This is generally true, regardless of whether the furnace is manually or automatically controlled, and regardless of the type of fuel employed. Modern heating systems are, however, preponderantly automatically controlled and operated, and it is toward such systems that the present invention is aimed, especially, automatic, gas-fired systems.
Therefore, one object of the present invention is to provide an improved method and apparatus for exhausting combustion gases from a furnace.
Another object of the present invention is to provide an apparatus and method useful for improving the operating efficiency of a furnace.
A still further object of the present invention is to provide an apparatus to reduce the amount of energy exhausted with the combustion gases from a furnace by impounding waste heat, increasing the CO.sub.2 content, lowering the CO and excess air to raise the temperature and lower the condensate in the exhaust chimney.
Other objects and advantages of the present invention will become apparent hereinafter.
An improvement in exhausting combustion gases from a furnace to achieve these objects has now been discovered. One embodiment of the present invention comprises a conduit means in fluid communication with the furnace for conducting combustion gases from the furnace to a chimney, the conduit means being appropriate in size and style to that for which the furnace was designed for voiding combustion gases. Also included is a flow redirection means located within the conduit means in the path of flow of combustion gases within the conduit means. This flow redirection means acts to change the direction of flow of at least a portion of the combustion gases flowing through the conduit means. The flow redirection means is designed so that the cross-sectional area available for gas flow at the location of the flow redirection means is at least as great as the cross-sectional area of the conduit means directly upstream or downstream of the flow redirection means.
The use of the present invention provides surprising benefits. The quantity of heat and uncombusted gases leaving the furnace with the combusted gases is reduced. At least a portion of the heat potential which is not lost in the combustion gases is available for effectively heating a heat-exchanger. In short, improved furnace efficiency, e.g., heating effectiveness, fuel economy, and the like, can be obtained by using the present invention.
The flow redirection means of the present invention may change the direction of only a portion of the combustion gases flowing through the conduit. Preferably, such flow redirection means changes the direction of flow of a major portion, if not all, of such combustion gases.
In a preferred embodiment, the flow redirection means comprises a flow baffle located substantially across the flow of combustion gases in the conduit, so that at least a portion of the gases are caused to flow around the flow baffle; and an added area located in association with the flow baffle provides cross-sectional area available for flow of combustion gases at the location of the flow baffle. In normal use, the flow baffle means is stationary. However, the flow baffle means is removable and replaceable by one of another size so that the amount or fraction of combustion gases redirected by the flow redirection means can be varied depending on the combustion requirements of the individual atmospheric burner.
As noted previously, the cross-sectional area available for the flow of combustion gas at the location of the flow redirection means is at least equal to, or preferably greater than, the cross-sectional area for combustion gas flow in the conduit directly upstream of the flow redirection means.
The cross-sectional area of the conduit for combustion gas flow is preferably substantially constant upstream of the flow redirection means. Preferably, the portion of the conduit down-stream from the flow redirection means also has a substantially constant gas flow cross-sectional area. Usually, the conduit has a substantially circular cross-section normal to the general direction of flow of combustion gases. Additionally, the general direction and volume of combustion gas flow, e.g., in the conduit, is substantially the same both upstream and downstream of the flow redirection means. In other words, the flow redirection means does not need to permanently change the flow direction or volume of combustion gases in order to perform its function in the present invention.
Under existing public utility and utility associations' standards for automatic gas-fired furnaces, no structure in the exhaust gas conduit, that reduces the effective area of the latter to a lesser area than that for which a furnace or combustion chamber is designed, is permissible during the operational period of the furnace. The present invention meets this requirement by interposing a baffle across the main body of exhaust flow in the effluent conduit from a combustion chamber at an enlarged chamber in said conduit, which, while being hermetically closed to the ambient atmosphere, is capable of receiving and forwarding the full volume of exhaust flow diverted into the chamber by the baffle without restriction or substantial pressure difference. The baffle, in diverting the flow, sets up eddy currents that increase the frictional resistance to the flow of the exhaust gases, causing an acceptable degree of retardation thereof, to effect a dwell in the products of combustion, and a momentary detainment of otherwise waste heat and fuel, in the combustion chamber. The augmented combustion cycle, with enhanced temperature and time parameters thus afforded, causes carbon monoxide (CO) and excess air still resident in the combustion chamber as the result of said baffle, to be converted to carbon dioxide (CO.sub.2 ), an exothermic reaction that further elevates the heat in the system, without regard to new fuel input from the supply source. This reduces excess air in the system, and also reduces condensation in the exhaust effluent.
These and other aspects and advantages of the present invention are set forth in the following detailed description and claims, particularly when considered in conjunction with the accompanying drawings in which like parts bear like reference numerals.